Electric relay



NOV. 6, 1934. J 1,979,317

ELECTRIC RELAY Filed March 23, 1933 lmo ll 20 22 INVENTOR. i Zea/A's 14"Cur-f/s 32 ATTORNEY Patented Nov. 6, 1934 UNITED STATES PATENT OFFICEApplication March 23, 1933, Serial No. 662,205

L 8 Claims.

My invention relates to improvements in re lays; and particularlyelectrical relays for enabling a supply circuit to be connected to awork circuit without risk of mishap or personal hazard when any of thedevices must be operated in the latter circuit with a definite relationto ground.

An object of the invention is to provide an electric relay adapted to beconnected to an alternating current supply circuit in a manner thatinsures closure of the relay when the leads of the work circuit areproperly united to the conductors of the supply circuit, but cannotresult in closure if the relation between said leads and said conductorsis reversed.

Another object of the invention is to provide an electric relay forconnecting a loud speaker to a source of signal voltage applied betweenthe neutral wire of a lighting circuit and the ac safety ground of thesystem, when a conducting plug is properly inserted in a lightingcircuit outlet; and for preventing the completion or closure of thecircuit if the plug is not properly inserted.

Another object of the invention is to provide a rectified current forenergizing the field of an electrodynamic loud speaker by means of athermionic tube, which also controls the operation of a protectiverelay.

The, above and other objects and advantages of the invention are clearlyset forth in the ensuing description and the novel features of myimprovement are defined in the appended claims. But this disclosure isexplanatory only without departing from the principle of the inventionor exceeding the scope of the terms in which the appended claims areexpressed.

On the drawing:

Fig. 1 is a diagrammatic view showing one form of my electrical relaycircuit; and

Fig. 2 shows another form.

The same numerals indicate the same parts throughout.

Referring first to'Fig. 1, I show a pair of conductors or mains 1connected to branch circuits 2 and 3. These branch circuits may havecurrent consuming devices therein and one of these branch circuits, suchas the circuit 3, is adapted to be connected so as, to supply current tomy improved electrical relay and enable the latter to be operatedtherefrom. In the line of each of the conductors 1 is a coil 4, the twocoils 4 being inductively related and serving as reactors in a manner asis set forth in the application,

and changes may be made in various ways of William F. Cotter and MarionE. Bond for a patent on a Program distribution system, Serial No.662,252, filed on even date herewith. The mains 1 may also be connectedto a watthour meter 5, with the reactors 4 between said meter and thebranch circuit 3. Electrical circuits for lighting and power areprovided with a safety ground where the circuit enters the customer'spremises, as shown at 25. The conthrough one of the mains 1 and thesafety ground to a loud speaker 9a in the circuit united to branch 3, aswill now be set forth. The method of connecting a radio receiver orother source of signals, not shown, to the circuit 2 and the advantageand purpose of such connection is fully disclosed in the application ofCotter and Bond aforesaid and is not part of the invention describedherein. My invention may, however, be employed not only to efiect properconnection of the loud speaker to the line 1, but also in the conductorsbetween the line and the receiver from which signals are impressed uponthe line, to insure proper connection of said receiver thereto.

The circuit 3 has the two sides thereof joined to a pair of terminals 7so that connection can be made between the terminals 7 and a pair ofterminals 8 of the circuit'of the relay system. The operating coils forthe loud speaker are indicated at 9 and 10, the body of the speakerbeing diagrammatically indicated adjacent these coils to reveal theirfunction. I prefer to describe my invention in connection with anelectrodynamic loud speaker including a speech coil and a field coil;the numeral 9 indicating the former and the numeral 10, the latter. Toprovide current from the mains 1 for the field coil 10, a rectifier 11of the vacuum tube type may be utilized. This tube has an anode 11aconnected by a wire 14 through one pair of terminals 7 and 8 to thegrounded side of the supply circuit 3. At 12 is indicated the primary ofa transformer, the secondary 13 of which supplies current to the heatercircuit of the tube for the cathode 110 when the primary is connected tothe supply Circuit by closing the on-oif switch 24. Connected to thewire 14 between the anode and the circuit 3 is a conductor 15, which mayinclude a fuse 23, leading to the movable contact 16 adapted to engage afixed contact joined to one terminal of the speech coil 9. The oppositeterminal of the coil 9 is to be grounded by a clip 18 adapted to engagea water pipe or any other convenient connection to the earth. The grid11!) of the tube is also connected to ground through a resistance 17.

One side of the switch 24 is also connected through a wire 19 and anindicator lamp 21 to one terminal of a relay coil 20. The other terminalof this coil 20 is joined to the dynamic field coil 10 which is furtherconnected to the cathode element of the vacuum tube. Coil 20 whenenergized draws up the contact 16 and closes the circuit from thegrounded side of the circuit 1 through the speech coil 9 to ground clip18.

A filter condenser 22 is connected across elements 10,20 and '21.

In operation the terminals 7 maybe part of an outlet connection or wallsocket and the ter-' minals 8 may be the tongues or prongs of the usualplug for such a socket connected by a cord to the primary winding 12 andthe leads 14 and 19 through the switch 24. The primary winding is thusconnected across the mains '1 and may supply alternating current atsuitable voltage to the filament of the vacuum tube.

When the connection is made as shown, so that the anode is united to thegrounded side of the supply circuit, rectified current is' provided bythe vacuum tube and the speaker is energized and gives forth the signalsimposed between the grounded side of the circuit 2, and earth. If,however, the connections between the terminals '7 and 8 are reversed, sothat the anode is connected to the ungrounded side of the supplycircuit, the tube will rectify insufficient current to operate therelay. Therefore no damage can result to the speech coil 9 as would bethe case if it were connected directly between the ungrounded side ofthe supply circuit 1 and ground. Thus the owner of the device can alwaysconnect the speaker to the supply line with perfect safety and withcomplete assurance that no mishap can take place. If the terminals 7 and8 are correctly joined, the coil 9 and the vacuum tube rectifier anodewill be connected to the grounded side of the supply circuit 1, and ifthese connections are reversed, no harm can be done, since the relaywill not close at all.

I can also utilize myinvention for safely connecting in a similar way toan alternating current supply circuit, any other circuit which requires,in order to give voltage to ground or to avoid personal hazard, that adefinite terminal of the connected device he at ground potential. In'Fig. 2, I show a pair of alternating current leads grounded at 25, andat 26 is an ordinary plug connector having terminals 2'7 and 28. Theconductors joined to these terminals are indicated at 29, the filamenttransformer having its primary 12 connected across these conductors andits secondary 13 leading to the heater of the vacuum tube rectifier asbefore. In one side of the circuit 29 is the switch 24 and this side .ofcircuit 29 is also connected by a lead 30 to a relay coil 20 in circuitwith the cathode of the rectifier. The same conductor is joined to thegrid of the rectifier'through a resistance 17 and between saidresistance and grid is a ground connection 18. The filter condenser 22is joined across the terminals of the relay coil 20 and this relay coil,when rectified current flows therethrough, actuates the movable contacts16 into engagement with fixed contacts 32. These contacts close a workcircuit indicated at 31 across the leads 29 which may include any deviceto be operated and at the same time protect it or the operator againstinjury in case the connections between the supply circuit and the relaycircuit are wrongly made. If the plug connector 26 is correctly unitedto the supply circuit 1, the rectifier will produce direct current andenergize the relay 20 to close the circuit 31. If, however, the plug 26is reversed, then the vacuum tube rectifier will not operate and therelay 20 will fail to close the contacts 16 and 32.

Thus in both the circuits of Figs. 1 and 2, the work circuit can beproperly controlled and is made to depend upon a specific connectionwith the supply circuit. The grid of the vacuum tube is always connectedto the ground and the relay coil or other load isin the cathode circuitand is operated by the current rectified by the tube. When the anode isalso connected to ground by the proper insertion of the plug, the gridand plate are at the same potential and the tube acts as a diode,passing rectified current from the anode to the cathode. The amount ofcurrent is determined by the resistance of the relay, voltage of theline, and other factors. When the plug is improperly connected to thesupply line the tube starts to rectify but builds up a negative bias onthe grid due to the resistance drop in the relay coil 20 or the coil 20and the field 10. The rectified current is then limited to a very smallvalue insufilcient to operate the relay because of said negative gridbias. The equipment to be protected is therefore not connected when theplug is improperly inserted.

Having described my invention, what I claim 1. The combination of analternating-current energizing circuit having one side grounded, a relaycoil, and means including a three electrode rectifier with anodeconnected to said grounded side and grid connected to ground, andconnections for enabling said coil to be energized only when properlyconnected to the energizing circuit, so that in the event of incorrectconnections no current flows in a circuit controlled by the relay.

2. The combination of an alternating-current energizing, circuit havingone side grounded, a circuit containing a relay and means including athree electrode rectifier with anode connected to said grounded side andgrid connected to ground, and connections for joining thelastnamed-circuit to the energizing circuit adapted to enable current toflow in the circuit of the relay only when the latter is properlyconnected to the energizing circuit.

3. The combination of an alternating-current energizing circuit havingone side grounded, a relaycoil and the speech coil and field coil of adynamic loud speaker and means including a three electrode rectifierwith anode connected to said grounded side and grid connected to ground,and connections adapted to enable current to be supplied to said'coilsonly when properly connected to the energizing circuit so that damage tothe speaker is avoided in case of improper connection.

f-49The combination of an alternating-current energizing circuit havingone side grounded, a relay coil, circuits containing said coil and in- 0eluding a three electrode rectifier with anode connected to saidgrounded side and grid connected to ground, and connections havingcontacts therein arranged to be closed only when said circuits areproperly connected to the energizing circuit.

5. The combination of an alternating-current energizing circuit havingone side grounded, a relay circuit having a three electrode vacuum tuberectifier therein, said rectifier having an anode adapted to beconnected to said grounded side and a grid connected to ground, and aconnection between the cathode and the opposite side of said energizingcircuit, a relay coil in said connection, a loud speaker field coil alsoin said connection, a conductor controlled by the relay coil extendingfrom the anode to the ground, a speech coil of a loud speaker in saidconductor and contacts controlled by said relay in said conductor.

6. The combination of an alternating-current energizing circuit havingone side grounded, a relay circuit connected thereto and having thereina three-element vacuum tube rectifier with an anode joined to saidgrounded side and a grid connected to ground, a permanent connectionbetween the grid of said tube and one side of the energizing circuit, arelay coil in circuit with the rectifier, and a circuit controlled bysaid relay.

7. The combination of an alternating-current energizing circuit havingone side grounded, a relay circuit, a three-element vacuum tuberectifier therein, said rectifier having an anode adapted to beconnected to said grounded side and a grid connected to ground, aconnection between the cathode and the opposite side of said energizingcircuit, a relay coil in said connection, a conductor extending fromsaid grounded side to ground, a speech coil of a loud speaker in saidlast-named conductor and contacts controlled by said relay coil in saidlast-named conductor.

8. The combination of an alternating-current energizing circuit havingone side grounded, a relay circuit connected thereto and having thereina three-element vacuum tube rectifier with an anode joined to saidgrounded side and a grid connected to ground, a permanent connectionincluding a resistance between the grid of said tube and one side of theenergizing circuit, a relay coil in circuit with the rectifier, and acircuit controlled by said relay.

LESLIE F. CURTIS.

